1,309 research outputs found
Spin drag Hall effect in a rotating Bose mixture
We show that in a rotating two-component Bose mixture, the spin drag between
the two different spin species shows a Hall effect. This spin drag Hall effect
can be observed experimentally by studying the out-of-phase dipole mode of the
mixture. We determine the damping of this mode due to spin drag as a function
of temperature. We find that due to Bose stimulation there is a strong
enhancement of the damping for temperatures close to the critical temperature
for Bose-Einstein condensation.Comment: 1 figur
Star Formation Histories of Nearby Elliptical Galaxies. II. Merger Remnant Sample
This work presents high spectroscopic observations of a sample of six
suspected merger remnants, selected primarily on the basis of H{\sc i} tidal
debris detections. Single stellar population analysis of these galaxies
indicates that their ages, metallicities, and -enhancement ratios are
consistent with those of a representative sample of nearby elliptical galaxies.
The expected stellar population of a recent merger remnant, young age combined
with low [/Fe], is not seen in any H{\sc i}-selected galaxy. However,
one galaxy (NGC~2534), is found to deviate from the -plane in the sense
expected for a merger remnant. Another galaxy (NGC~7332), selected by other
criteria, best matches the merger remnant expectations.Comment: 12 pages, 10 figures, accepted by A
Interaction effects on dynamic correlations in non-condensed Bose gases
We consider dynamic, i.e., frequency-dependent, correlations in non-condensed
ultracold atomic Bose gases. In particular, we consider the single-particle
correlation function and its power spectrum. We compute this power spectrum for
a one-component Bose gas, and show how it depends on the interatomic
interactions that lead to a finite single-particle relaxation time. As another
example, we consider the power spectrum of spin-current fluctuations for a
two-component Bose gas and show how it is determined by the spin-transport
relaxation time.Comment: 9 pages, 3 figure
The Westerbork HI Survey of spiral and irregular galaxies III: HI observations of early-type disk galaxies
We present HI observations of 68 early-type disk galaxies from the WHISP
survey. They have morphological types between S0 and Sab and absolute B-band
magnitudes between -14 and -22. These galaxies form the massive, high
surface-brightness extreme of the disk galaxy population, few of which have
been imaged in HI before.
The HI properties of the galaxies in our sample span a large range; the
average values of M_HI/L_B and D_HI/D_25 are comparable to the ones found in
later-type spirals, but the dispersions around the mean are larger. No
significant differences are found between the S0/S0a and the Sa/Sab galaxies.
Our early-type disk galaxies follow the same HI mass-diameter relation as
later-type spiral galaxies, but their effective HI surface densities are
slightly lower than those found in later-type systems.
In some galaxies, distinct rings of HI emission coincide with regions of
enhanced star formation, even though the average gas densities are far below
the threshold of star formation derived by Kennicutt (1989). Apparently,
additional mechanisms, as yet unknown, regulate star formation at low surface
densities.
Many of the galaxies in our sample have lopsided gas morphologies; in most
cases this can be linked to recent or ongoing interactions or merger events.
Asymmetries are rare in quiescent galaxies. Kinematic lopsidedness is rare,
both in interacting and isolated systems.
In the appendix, we present an atlas of the HI observations: for all galaxies
we show HI surface density maps, global profiles, velocity fields and radial
surface density profiles.Comment: 24 pages, 11 figures. Accepted for publication in A&A. A version with
the full atlas can be downloaded from
http://www.astro.rug.nl/~edo/WHISPIII.ps.gz (gzipped postscript, 9.3Mb
Active region contributions to the solar wind over multiple solar cycles
Both coronal holes and active regions are source regions of the solar wind.
The distribution of these coronal structures across both space and time is well
known, but it is unclear how much each source contributes to the solar wind. In
this study we use photospheric magnetic field maps observed over the past four
solar cycles to estimate what fraction of magnetic open solar flux is rooted in
active regions, a proxy for the fraction of all solar wind originating in
active regions. We find that the fractional contribution of active regions to
the solar wind varies between 30% to 80% at any one time during solar maximum
and is negligible at solar minimum, showing a strong correlation with sunspot
number. While active regions are typically confined to latitudes
30 in the corona, the solar wind they produce can reach
latitudes up to 60. Their fractional contribution to the solar
wind also correlates with coronal mass ejection rate, and is highly variable,
changing by 20% on monthly timescales within individual solar maxima. We
speculate that these variations are primarily driven by coronal mass ejections
causing global reconfigurations of the coronal magnetic field on sub-monthly
timescales.Comment: Pre-review copy; comments and suggestions welcome to the lead autho
Instaseis: instant global seismograms based on a broadband waveform database
We present a new method and implementation (Instaseis) to store global Green's functions in a database which allows for near-instantaneous (on the order of milliseconds) extraction of arbitrary seismograms. Using the axisymmetric spectral element method (AxiSEM), the generation of these databases, based on reciprocity of the Green's functions, is very efficient and is approximately half as expensive as a single AxiSEM forward run. Thus, this enables the computation of full databases at half the cost of the computation of seismograms for a single source in the previous scheme and allows to compute databases at the highest frequencies globally observed. By storing the basis coefficients of the numerical scheme (Lagrange polynomials), the Green's functions are 4th order accurate in space and the spatial discretization respects discontinuities in the velocity model exactly. High-order temporal interpolation using Lanczos resampling allows to retrieve seismograms at any sampling rate. AxiSEM is easily adaptable to arbitrary spherically symmetric models of Earth as well as other planets. In this paper, we present the basic rationale and details of the method as well as benchmarks and illustrate a variety of applications. The code is open source and available with extensive documentation at www.instaseis.net
Instaseis: instant global seismograms based on a broadband waveform database
We present a new method and implementation (Instaseis) to store global Green's functions in a database which allows for near-instantaneous (on the order of milliseconds) extraction of arbitrary seismograms. Using the axisymmetric spectral element method (AxiSEM), the generation of these databases, based on reciprocity of the Green's functions, is very efficient and is approximately half as expensive as a single AxiSEM forward run. Thus, this enables the computation of full databases at half the cost of the computation of seismograms for a single source in the previous scheme and allows to compute databases at the highest frequencies globally observed. By storing the basis coefficients of the numerical scheme (Lagrange polynomials), the Green's functions are 4th order accurate in space and the spatial discretization respects discontinuities in the velocity model exactly. High-order temporal interpolation using Lanczos resampling allows to retrieve seismograms at any sampling rate. AxiSEM is easily adaptable to arbitrary spherically symmetric models of Earth as well as other planets. In this paper, we present the basic rationale and details of the method as well as benchmarks and illustrate a variety of applications. The code is open source and available with extensive documentation at www.instaseis.net
Facing Forward, Nine stories about being a survivor of human trafficking in a post-trafficking shelter in the Netherlands
This report describes nine stories of six women and three men who recently exited a human trafficking
situation and, at the time of this research, resided in a shelter for foreign victims of trafficking
in the Netherlands. It speaks about their hopes and dreams, their fears and frustrations, and
describes how they feel social and health care might be improved. The report’s aim is to shed more
light on service users’ views on post-trafficking service provision for everyone directly (e.g. social
workers, psychologists and general practitioners) and indirectly (e.g. managers and policymakers)
involved with providing care to this group.
The main message from the report is that victims of human trafficking in a post-trafficking shelter
can be expected to exhibit a strong desire to move forward and establish a meaningful life with a
job, a family and friends. This is an important conclusion: it shows that besides the ‘trauma’-narrative
that is often stressed in the literature as being important among trafficking survivors, the
‘future‘-narrative is as important and should be taken into account in developing social and health
services for this group. Despite the importance of being able to pursue a meaningful life to them,
service users in this study were often stunted in doing just that. Through barriers in finding work,
education and a place to live, often caused by their residency status, a feeling of being ostracized
in Dutch society and shelter policies, service users often felt ‘in limbo’: standing still, without being
able to change that situation. Regardless of this, and seemingly against all odds, service users still
pursued their goals, by engaging in Dutch language courses, participating in vocational skills training
and engaging in volunteer work. These activities were described as useful by participants and therefore
preferable over other activities. Service users found them useful because they provided them
with opportunities to work towards their envisioned futures.
Hoping for the fulfilment of their goals and pursuing them in these ways likely allowed service users
to better cope with their problems in the present and improved their well-being. For this reason,
it is essential that social and health provision for this group supports and facilitates service users’
forwards-facing, future-orientated views, in addition to providing trauma-informed services. But
do not take our word for it: please read the stories in this report and get to know these men and
women, and read about what they, in their own words, feel service provision ought to look like in a
post-trafficking shelter
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